A viscoplastic-coupled phase field modelling for mechanical behaviors of thermal barrier coating system with randomly microporous structures

In this study, we have introduced a novel viscoplastic-coupled phase field approach to simulate the deformation and failure progression of thermal barrier coating systems (TBCs) with disordered microporous structures. The theory has been incorporated in the finite element method, for the first time, to characterize crack initiation and propagation in TBCs, considering both time-dependent deformations and tension–compression asymmetry mechanical behaviors. Furthermore, we have proposed a numerical framework for failure modeling of porous solids, which includes the quantitative characterization of microstructures, the parametric finite element modeling, and the visualization of calculation outcomes. We have performed several simulations of different microstructures, which have been compared against experimental data, demonstrating the predictive capabilities of our method in intricate structures. Our findings have revealed that cracks tend to emerge from nearby micropores, and an increase in porosity can lead to earlier crack initiation and a decrease in TBCs strength. Furthermore, micropores in the same horizontal line tend to cause cracks to propagate more easily, resulting in a substantial reduction in strength. For TBCs exposed to cyclic loading and thermal growth oxidation (TGO) growth stress, interfacial cracks are primarily caused by the deflection of cracks in the top coat (TC) layer. The method presented in this study offers a fresh perspective on the failure mechanism of solids with complex microstructures and contributes to the mechanical improvement of TBCs based on structural considerations.